As is known, car rear lights normally comprise a rigid, substantially tub-shaped rear casing which fits firmly inside a seat in the rear of the vehicle body; a front lenticular half-shell made at least partly of transparent or semitransparent, usually coloured, plastic material, and which closes the casing opening and emerges outside of the vehicle body; a number of substantially parabolic cup-shaped bodies located/formed in the rear casing, with their concavities facing the front lenticular half-shell, and each aligned with a respective transparent or semitransparent portion of the front lenticular half-shell; and a number of incandescent bulbs, each located at the bottom of a respective cup-shaped body to only backlight the transparent or semitransparent portion of the half-shell aligned over the cup-shaped body. The inner surface of each cup-shaped body is usually mirrored to focus the light from the incandescent bulb onto the corresponding transparent or semitransparent portion of the front lenticular half-shell.
Over the past few years, car rear lights have become increasingly integrated in the outer contour of the vehicle body, even to the point of wrapping round the two edges between the rear and sides of the car body, thus making it necessary to employ highly complex three-dimensional front lenticular half-shells.
In addition, leading car manufacturers have also begun demanding rear lights in which the light signals issue from long, narrow portions of the front lenticular half-shell.
To begin with, this was only demanded of low-intensity light signals used at night to indicate the position/presence of the vehicle, i.e. for parking lights, so most car rear light manufacturers opted to form long, narrow, transparent or semitransparent portions on the front lenticular half-shell of the light, and to backlight these strip-shaped transparent or semitransparent portions using light guide bars made of photoconductive material, and each of which extends beneath the front lenticular half-shell, and is substantially the same width as, and extends the full length of, the corresponding strip-shaped portion for backlighting.
More specifically, each light guide bar receives light from one or more light-emitting diodes, traditionally named LEDs, located on one of the two ends of the bar normally located far from the transparent or semitransparent portion to be backlighted, and is designed so that the light from the LED comes out gradually and in controlled manner from the lateral surface of the bar directly facing the front lenticular half-shell, so as to backlight the whole length of the transparent or semitransparent portion of the half-shell.
Unfortunately, being unable to produce high-intensity light beams, this system of backlighting strip-shaped portions of the front lenticular half-shell failed to meet later demand by car manufacturers for the same design for high-intensity light signals indicating operation of the vehicle's brake system, i.e. for the stop lights.
To produce a strip-shaped light signal of automotive regulation intensity, most car rear light manufacturers therefore opted to install, beneath the strip-shaped transparent or semitransparent portion/s of the front lenticular half-shell associated with the stop signal, a strip of high-efficiency LEDs of the same shape as the transparent or semitransparent portion for backlighting, and capable of producing a sufficiently homogeneous, intense light beam.
Unfortunately, to accommodate both backlighting systems in the light, and achieve from both light signals a field depth and visibility comparable with those of a normal incandescent bulb, relatively high-cost design solutions are required, which seriously increase the manufacturing cost of automotive lights of this sort, with all the problems this entails.